Mass/Time - IV mL Rate Questions

Give an order in quantity of mass per time, determine the necessary IV flow rate in mL/hr based on the given mass per volume. These types of problems are often used in critical care nursing.

Formula:
Ordered Per Hour
Have
x Volume (mL)  =  Y (Flow Rate in mL/hr)

Example: Give patient 500 mg of dopamine in 250 mL of D5W to infuse at 20 mg/hr. Calculate the flow rate in mL/hr.
Ordered Per Hour
Have
x Volume (mL)  =  Y (Flow Rate in mL/hr)
20 mg/hr
500 mg
x 250 mL  =  10 mL/hr

Example: Aggrastat at 12.5 mg in 250 mL is prescribed to be infused at a rate of 6 mcg/kg/hr in a patient who weighs 100 kg. At what flow rate in mL/hr will you set the pump?
Ordered Per Hour
Have
x Volume (mL)  =  Y (Flow Rate in mL/hr)
  • The first step is to convert the order per time to the amount required for this particular patient. This is a Dosage By Weight Question. 100 kg is the weight in kg and 6 mcg/kg/hr is a dosage in terms of kg.
Weight in Kg * Dosage Per Kg  =  Y (Required Dosage)
100 kg * 6 mcg/kg/hr  =  600 mcg/hr
Convert 600 mcg/hr to mg/hr.
  • mcg → mg → g → kg    ( ÷ by 1,000 )
  • 600 ÷ 1,000 = 0.6 mg/hr
0.6 mg/hr
12.5 mg
x 250 mL  =  12 mL/hr

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